Localized and episodic enhancement of net community production and phytoplankton carbon in spring and summer at the Northeastern US shelf‐break front

The shelf‐break front of the Mid‐Atlantic Bight (MAB) is hypothesized to cause increased biological productivity but observations of such enhancement have been scarce. Additionally, most previous studies at the MAB are based on chlorophyll rather than on actual observed rates of production. Here we present rates of net community production (NCP) and concentrations of phytoplankton carbon, collected at high spatial resolution (< 1 to 3 km) on repeated crossings of the shelf‐break front in spring and summer during 4 yr on the Northeastern US Shelf. We find a localized 50% increase in NCP within 5 km of the shelf‐break front on a majority of transects in early spring; there is a smaller and less frequent increase during later spring and summer. Phytoplankton carbon usually increased very close to the shelf‐break front in the same transects. These data provide an unprecedented look at spatial patterns in productivity rates at the shelf‐break front and show that strong increases in productivity occur at the front but also that such responses are likely short‐lived and occur over short spatial scales, explaining why they may have been missed in other studies.